In this article Stuart Christian, Director of Greener Waste Limited explains how a simple, low cost process can dramatically improve the performance of failing filter beds.

Filter beds are a simple and effective way of reducing the organic loading within wastewater in a carbon footprint friendly manner. A simple filter bed is made up of a media layer, for instance broken blast furnace slag, laid on top of drainage tiles to a depth of approximately 1.75 metres, the whole of which sits on a concrete base with a central drainage channel leading to a collection sump.

Media size is an important element in the treatment process to ensure an adequate supply of oxygen. The gap between the media must be sufficient to allow water to pass down while air and therefore oxygen pass up. Wastewater is continually spread over the top of the bed by a distribution mechanism, allowed to run down through the bed and out through the bottom outlet channel. As the wastewater passes over the media, oxygen in the air enables bacteria to grow and form a film on the media. It is the bacteria that digest the organic matter within the wastewater.

In this article Stuart Christian, Director of Greener Waste Limited explains how The Bio-Selector bio-augmentation system can benefit the operation of small wastewater treatment works.

Once regarded as the main process option for the wastewater treatment for small communities, circular biological filters, so common on the outskirts of towns for many years, provided a reliable low cost and low profile method of treating household wastewater. Quiet and robust, their simple engineering and structural design could be easily maintained by a daily visit from an operator, who, on the smaller sites, only needed a couple of hours to carry out essential duties. Principal operating tasks involved de-sludging the primary and humus tanks, the remaining requirements revolved around general maintenance.

As new technology has developed, more opportunities for automation such as motorised distribution arms and automated de-sludging have occurred reducing the requirement for daily visits. However the lack of consistent site attendance can have an adverse effect on small remote works. The old daily rituals of weeding and pricking out often become neglected leading to inefficient distribution and build up of gross solids within the top surface of the beds, particularly if the media starts to deteriorate.